Aryloxy leaving groups

Scheme 5 A proposed concerted mechanism for methoxide promoted methanolysis of carboxylate esters with displacement of aryloxy leaving groups.

Again, evidence is lacking on the merit of aryloxy leaving groups in phosphinites, but one would suspect rapid cleavage to generate the resonance-stabilized aryloxy anion. ... 

An important group of acylation reactions involves esters, in which case the leaving group is alkoxy or aryloxy. The self-condensation of esters is known as the Claisen condensation.216 Ethyl acetoacetate, for example, is prepared by Claisen condensation of ethyl acetate. All of the steps in the mechanism are reversible, and a full equivalent of base is needed to bring the reaction to completion. Ethyl acetoacetate is more acidic than any of the other species present and is converted to its conjugate base in the final step. The (3-ketoester product is obtained after neutralization. 

An important group of these reactions involves esters, in which case the leaving group is alkoxy or aryloxy. The self-condensation of esters is known as the Claisen condensation. 118 Ethyl acetoacetate, for example, is prepared by Claisen condensation of ethyl... 

Aryloxy groups have also been used as leaving groups. Reaction of 1-chloro- and l-methanesulfonyl[l,4]benzo-dioxino[2,3-r/]pyridazine 164 and 4-chloro[l,4]benzodioxino[2,3-Hpyridazine with NaOMe afforded ring-opened and cyclized pyridazines (Scheme 40). Their reaction with amines afforded 1-substituted [l,4]benzodioxino[2,3-rf]pyr-idazines 165, 4-substituted [l,4]benzodioxino[2,3-f]pyridazines 166, and/or 2-hydroxyphenoxypyridazines 167 (Scheme 41) <2004H(63)591>. 

The epimeric substituted aryloxy phosphorinanes 2- were hydro lyzed in 30% dioxane/water at 70 C with a variety of nucleophiles (11). The reactivities were sensitive to changes in both the nucleophile and leaving group. The Bronsted 6 s for the... 

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